Cabbage White Caterpillars (Small White)

August 28, 2017

A few weeks ago I discovered a bunch of butterfly eggs all over a nasturtium plant and decided to take an eggy leaf in the house so that I could watch the caterpillars develop.

At first I identified the eggs as belonging to Large (White) Cabbage White Butterflies as I saw the adults fluttering around the nasturtium plant and the eggs were very similar to those of the large white, however the eggs weren’t laid in clusters which I found very odd. As it turns out, this behavior is normal for Small (White) Cabbage White Butterflies and that’s what they were!

The adult butterflies are remarkably similar in addition to laying similar looking eggs and the larva of both butterflies eat the same plants too, however the caterpillars look nothing alike. In 2015 I took 23 large white caterpillars into my house to observe with my daughter and I’ve got that whole event thoroughly documented HERE.

Below I have documented my entirely less traumatic, small white adventure with lots of photos!

The above photo is of a small white caterpillar (green) and a large white caterpillar (black and yellow) next to each other to demonstrate how very different they look.

This time I harvested the leaf before the eggs had hatched so that there would be no chance of parasitic wasp explosions. There were 11 eggs on the leaf and they all hatched over the course of about four days.

The tiny caterpillars start out yellow and they immediately eat the egg after hatching. Afterwards, most also ate a tiny hole in the leaf where the egg was attached before resting.

When resting the caterpillars would usually lie along a leaf vein for camouflage which made them really difficult to spot in the first few days especially since they also turn green after they’ve filled themselves with leaf.

I rarely saw the caterpillars eating when they were small. When I had my large white caterpillars they never seemed to stop moving, however most of them were afflicted by parasitic wasp larva, so I don’t know how much the wee lodgers would have affected their eating behavior.

After a week the caterpillars were roughly a half inch long, quite pudgy and much easier to spot. I noticed that their basic behavioral pattern was to gorge themselves, then assume a resting position for several minutes until they did a big poop, at which point they came to life again and resumed gorging themselves.

I didn’t really witness them shedding their skins the same as I did with the large whites, however I could tell when they were about to moult as they would get very rigid and shiny. I believe that the reason why I rarely saw the skins s is because small white caterpillars eat their skin after it’s shed, whereas the large whites abandon their furry, black skin after it is shed.

Large white caterpillars also will go to a special place to moult whereas small whites just do it in their normal resting positions, usually laying along the vein of the leaf they are currently feeding on.

Once they got over about a half inch long they became more bold and I observed them eating often. I never touched them, but I did occasionally remove a leaf that they were feeding on so that I could watch them more closely. They didn’t seem to notice at all.

After I had the eating machines for 2 weeks the oldest ones were approaching their full size of about an inch and a quarter.

Everywhere they crawled they swayed their heads from side to side laying down fine webs of silk. The silk trails could be seen all over the leaves.

These caterpillars are quite transluscent and if you look really closely at the video below you can see the green pulse running up and down their backs. I apologize for the less than great quality of the video, my phones camera is garbage. You can also see one caterpillar eating and another swaying its head as it lays down a path of silk from the glands beneith its mouth. You can also see the trail of silk that it has left behind.

On day 14 the oldest left the leaf and made its way to the top of the container to prepare for pupation. Before it was time to pupate none of the caterpillars explored any of the container aside from the leaves they were feeding on. This is another point where they differed greatly from the large white caterpillars who were quite curious by comparison.

The pupation part of the caterpillars life cycle was almost identical to what I had observed with the large white caterpillars.

First they choose a spot, far away from their food usually at the top of the container, and they lay down a bed of silk very slowly.

Next they rest until they completely evacuate their bowels so that they are empty and then deposit a concentrated point of silk which they secure their back end to.

After the back end is secured they make two more concentrated points of silk on either side of the body and wrap the threads around themselves several times to form a sort of harness that tethers the body to the silk net

You can see the three dots of white around the caterpillar in the photo above. Once the caterpillar is finished this whole process, which takes roughly a day, the total size of it has been reduced by about a third.

After about another 24 hours it will shed its skin to reveal a bright green jaggy looking chrysalis. The chrysalis is roughly half the size of the full grown caterpillar. It is quite bizarre seeing how small it manages to shrink! Over the next few days the chrysalis turns brown to resemble a dead leaf.

I really like the above photo because it demonstrates 4 stages of the caterpillars changing. Below are some close up images I managed to get as well.

Some of my happiest moments in life are spent observing insects.

I know that a lot of people out there (particularly farmers) view these bugs as nothing but pests, however I can’t help but see the beauty in them at every stage of life. And how freaking cool is it that something can break down into what is essentially stem cell soup within its own skin to become something entirely different? Butterfly life cycles are nothing short of amazing. and I am so happy that I can share them with my children up close and personal.

There are 9 pupated caterpillars in total, (no idea what happened to the other 2) and if you would like to see what happened next…. click HERE :D